xref-code 0.3.0

Ultra blazing fast cross-references, layout recovery, slicing & pseudo-C for x86-64 ELF and Mach-O binaries, plus live Linux process inspection
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174

/*
 * xref — Ultra blazing fast cross-references of an x86-64 ELF binary
 * Copyright (c) 2026 Alexander Panasenko
 *
 * Contact: alex@prod.codes
 * Author: https://prod.codes/about/
 * SPDX-License-Identifier: MIT OR Apache-2.0
 */

//! Function listings: the ordered calls of a function and its annotated disassembly.

use std::io::Write;
use std::ops::Range;

use iced_x86::{FlowControl, Instruction};

use crate::commands::{Res, function};
use crate::image::{Image, Slot};
use crate::scan::{branch_target, decode, format};

/// A code address with the function or PLT import stub it starts or lies in.
pub fn describe_code(image: &Image, target: u64) -> String {
    match image.function_at(target) {
        Some(f) if f.start == target => format!("{target:#x}"),
        Some(f) => format!("{target:#x} (in {:#x}+{:#x})", f.start, target - f.start),
        None => crate::runtime::plt_import(image, target)
            .map_or_else(|| format!("{target:#x} (no function)"), |imp| format!("{target:#x} ({imp})")),
    }
}

/// Where a call or jump goes: a direct target, an imported symbol or pointer slot, or a register.
pub fn describe_branch(image: &Image, instruction: &Instruction) -> String {
    if let Some(target) = branch_target(instruction) {
        return describe_code(image, target);
    }
    if instruction.is_ip_rel_memory_operand() {
        let place = instruction.ip_rel_memory_address();
        return match image.slot(place) {
            Some(Slot::Import(name)) => format!("{name} via {place:#x}"),
            Some(Slot::Pointer(target)) => format!("{} via {place:#x}", describe_code(image, target)),
            None => format!("[{place:#x}]"),
        };
    }
    format!("indirect: {}", format(instruction))
}

/// A call, or a jump leaving `function` (a tail call).
pub fn is_call(instruction: &Instruction, function: &Range<u64>) -> bool {
    match instruction.flow_control() {
        FlowControl::Call | FlowControl::IndirectCall => true,
        FlowControl::UnconditionalBranch => branch_target(instruction).is_some_and(|t| !function.contains(&t)),
        FlowControl::IndirectBranch => instruction.is_ip_rel_memory_operand(),
        _ => false,
    }
}

pub fn calls(image: &Image, addr: u64, out: &mut dyn Write) -> Res {
    let f = function(image, addr)?;
    let code = image.code(&f).ok_or("function outside the image")?;
    let mut lines = Vec::new();
    decode(code, f.start, |instruction| {
        if is_call(instruction, &f) {
            let kind = if instruction.flow_control() == FlowControl::Call
                || instruction.flow_control() == FlowControl::IndirectCall
            {
                "call"
            } else {
                "jump"
            };
            lines.push(format!("{:#x}  {kind} {}", instruction.ip(), describe_branch(image, instruction)));
        }
    });
    writeln!(out, "function {:#x}..{:#x}", f.start, f.end)?;
    for line in &lines {
        writeln!(out, "{line}")?;
    }
    writeln!(out, "{} calls", lines.len())?;
    Ok(())
}

fn annotation(image: &Image, instruction: &Instruction, function: &Range<u64>) -> Option<String> {
    if is_call(instruction, function) {
        return Some(describe_branch(image, instruction));
    }
    if !instruction.is_ip_rel_memory_operand() {
        return None;
    }
    let place = instruction.ip_rel_memory_address();
    match image.slot(place) {
        Some(Slot::Import(name)) => Some(name.to_owned()),
        Some(Slot::Pointer(target)) => Some(
            image.preview(target).map_or_else(|| format!("-> {target:#x}"), |text| format!("-> {target:#x} {text:?}")),
        ),
        None => image.preview(place).map(|text| format!("{text:?}")),
    }
}

pub fn asm(image: &Image, addr: u64, from: Option<u64>, to: Option<u64>, out: &mut dyn Write) -> Res {
    let f = function(image, addr)?;
    let code = image.code(&f).ok_or("function outside the image")?;
    let shown = from.unwrap_or(f.start)..to.unwrap_or(f.end);
    let mut lines = Vec::new();
    decode(code, f.start, |instruction| {
        if shown.contains(&instruction.ip()) {
            let text = format(instruction);
            let ip = instruction.ip();
            lines.push(
                annotation(image, instruction, &f)
                    .map_or_else(|| format!("{ip:#x}  {text}"), |note| format!("{ip:#x}  {text:<48} ; {note}")),
            );
        }
    });
    writeln!(out, "function {:#x}..{:#x}", f.start, f.end)?;
    for line in &lines {
        writeln!(out, "{line}")?;
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::{asm, calls, describe_code, is_call};
    use crate::image::{Image, Segment};
    use crate::scan::decode;

    fn instructions(bytes: &[u8], ip: u64) -> Vec<iced_x86::Instruction> {
        let mut all = Vec::new();
        decode(bytes, ip, |instruction| all.push(*instruction));
        all
    }

    #[test]
    fn calls_include_tail_jumps_but_not_local_jumps() {
        // call +0; jmp +0 (to the next instruction, inside); jmp rel32 far away; jmp rax.
        let code = [0xe8, 0, 0, 0, 0, 0xeb, 0x00, 0xe9, 0x00, 0x10, 0, 0, 0xff, 0xe0];
        let function = 0x1000..0x1000 + code.len() as u64;
        let flags: Vec<bool> = instructions(&code, 0x1000).iter().map(|i| is_call(i, &function)).collect();
        assert_eq!(flags, [true, false, true, false]);
    }

    #[test]
    fn listings_annotate_imports_pointers_and_tail_jumps() {
        let mut data = vec![0u8; 0x300];
        data[0x100..0x108].copy_from_slice(b"text msg");
        // jmp [rip + 0x100] (import); call [rip + 0x110] (ptr); call [rip + 0x120] (raw);
        // lea rax, [rip + 0x100] (import); lea rax, [rip + 0x110] (ptr->text); lea rax, [rip + 0x118] (ptr->code);
        let code: &[u8] = &[
            0xff, 0x25, 0xfa, 0x00, 0x00, 0x00, // 0x1000: jmp [0x1100] (import)
            0xff, 0x15, 0x04, 0x01, 0x00, 0x00, // 0x1006: call [0x1110] (ptr)
            0xff, 0x15, 0x0e, 0x01, 0x00, 0x00, // 0x100c: call [0x1120] (none)
            0x48, 0x8d, 0x05, 0xe7, 0x00, 0x00, 0x00, // 0x1012: lea rax, [0x1100] (import)
            0x48, 0x8d, 0x05, 0xf0, 0x00, 0x00, 0x00, // 0x1019: lea rax, [0x1110] (ptr->text)
            0x48, 0x8d, 0x05, 0xf1, 0x00, 0x00, 0x00, // 0x1020: lea rax, [0x1118] (ptr->raw)
        ];
        data[..code.len()].copy_from_slice(code);
        let end = 0x1000 + code.len() as u64;
        let image = Image {
            data,
            segments: vec![Segment { va: 0x1000, offset: 0, size: 0x300 }],
            functions: std::iter::once(0x1000..end).collect(),
            pointers: vec![(0x1110, 0x1100), (0x1118, 0x1200)],
            imports: vec![(0x1100, "puts".to_owned())],
            symbols: Vec::new(),
            metadata: crate::image_format::Metadata::default(),
        };
        assert_eq!(describe_code(&image, 0x1002), "0x1002 (in 0x1000+0x2)");
        assert_eq!(describe_code(&image, 0x9000), "0x9000 (no function)");
        let mut out = Vec::new();
        assert!(calls(&image, 0x1000, &mut out).is_ok());
        assert!(asm(&image, 0x1000, None, None, &mut out).is_ok());
        let text = String::from_utf8_lossy(&out);
        assert!(text.contains("jump puts via 0x1100") && text.contains("-> 0x1200"), "{text}");
    }
}